1. Field of the Invention
The present invention relates to an encapsulated glazing, a primer composition for treating a glazing and a process for the adhesion of a thermoplastic profile to a glazing. This profile can be obtained by different processes, such as encapsulation or extrusion. The profile can, in particular, be formed on the periphery of the glazing. However, the profile can also be formed at any other point or area of the glazing (e.g., with a view to the bonding of the base of a driving mirror).
2. Discussion of the Background
The present invention is of a general nature. However, it may be most easily understood by examining the process of encapsulating or overmolding a glazing with a thermoplastic profile (or joint).
Glazings, particularly car glazings, can be encapsulated in two ways. The first method is the reactive injection molding (RIM) process, which consists of injecting a reaction mixture of two components into a mold in order to form a thermosetting polymer on the periphery of the glazing. For example, injection of a polyol component and an isocyanate component forms a polyurethane as the encapsulation joint. However, this method suffers from the disadvantage of requiring relatively sophisticated molds, which leads to relatively high production costs.
Another method consists of injecting a thermoplastic material to produce an overmolding profile on the glazing. Costs are lower than in the case of the RIM process. The thermoplastic injection method nevertheless requires high pressures. It is therefore not very suitable for large glazings such as rear windows or car windshields, which may break under such high pressures. However, it is completely suitable for small glazings, such as car side windows.
A currently used thermoplastic material is polyvinyl chloride (PVC). However, the presence of chlorine in the PVC encapsulation joints introduces problems, particularly when recycling the plastic materials. In addition, PVC compositions incorporate plasticizers, which can ruin some paints conventionally used for automobile bodies.
If one was to try to replace PVC with a different thermoplastic material, more specifically an olefinic thermoplastic (i.e., having an olefin matrix), such as ethylene, propylene, or a copolymer thereof, one would encounter the disadvantage of the poor affinity of the olefinic thermoplastic with other materials, and in particular, with glass, due to the apolar nature of these thermoplastic materials.